This invention relates generally to position adjusters for seats and/or windows, particularly for use in motor vehicles. The adjuster is of the type having hinge mount levers joined together by a rotary shaft, an inner gear connected to one lever and a spur gear ring connected to the other lever and being in mesh with the inner gear, the crown circle of the spur gear ring being smaller at least about one tooth than the root circle of the inner gear, and one of the levers being supported for rotation on an eccentric connected for joint rotation with the driven shaft.
Adjusters of this kind are employed in hinge mounts for seats having reclinable back rests, whereby one of the mount levers is connected to the seat proper, and the other mount lever is connected to the back rest. In rotating the eccentric the spur gear ring is rolled in mesh with the inner gear and consequently an inclination corresponding to the difference between the teeth of the two gears is imparted to the hinged lever, whereby this angular position adjustment is performed continuously and the resulting adjuster is simple in structure, occupies minimum space and can be exposed to high loads. In addition, due to the different number of teeth between the meshing gears and due to the corresponding eccentricity of the eccenter a self-locking effect between the wobbling gears is achieved, thus ensuring that the adjuster is reliably held in any adjusted position and the backrest itself even under extreme overloads cannot be unintentionally released. These known hinge mounts are therefore very advantageous. Nevertheless, in order to secure a comfortable manipulation of the adjuster, a considerable lateral and radial play must be provided between the meshing teeth of the inner gear and of the spur gear ring, which in response to the rotary movement of the eccenter performs a rolling or wobbling movement in the inner gear. Due to the unavoidable tolerances occurring during mass production, this relatively large radial play may become still larger and, as a result, the hinge mount assembly, particularly when the backrest is not under load, may produce rattling noises due to vibrations occurring upon the starting of the vehicle.
Apart from the aforedescribed application of these hinge mounts for the angular position adjustment of a backrest, it is also known to employ these adjusters for setting the vertical or longitudinal position of the seat. In a known device for adjusting the vertical position of the seat, a pair of scissors-like two-arm mount levers is connected to lateral sides of each seat proper. In the region of crossing of each pair of levers, an adjusting and locking device in the form of wobble gears is arranged, whereby the wobble gears are controlled similarly to the preceding adjuster by means of an eccentric rigidly mounted on a driven rotary shaft. This rotary shaft also joins the crossing parts of the levers in axial direction. Since the hinge mount levers are to be free from the wobbling movement of the gears in the adjusting mechanism, the gear supported on the eccentric is pivotally connected via a pin to the assigned hinge mount lever, whereby the pin engages an oblong slit in the lever so as to permit the movement of the eccentric. At the same time, both mount levers are supported for rotation about a common axis on the shaft. Each mount lever in this vertical position adjusting device is secured at one end thereof to the seat proper and at the other end is supported on a floor rail. Even this known vertical position adjusting device requires considerable radial play which still can be increased due to manufacturing tolerances between the teeth and bearings of the gears, resulting in rattling noises during the motion of the vehicle when the seat is unloaded.
Moreover, the adjusters of the aforedescribed type can be also used in windows lifters for motor vehicles whereby one hinge mount lever is secured to the body of the motor vehicle, whereas the other mount arm acts as an adjustment arm cooperating in a known manner with the window. The hinge mount levers, even in this application, are mutually joined by means of a shaft which is again provided with an eccentric for transmitting rotary movement to an input gear of a wobble gear type adjusting and locking device for determining the position of the two hinge parts. Similarly as in the preceding examples, the teeth of the inner gear connected to one hinge mount lever and of the spur gear connected to the other lever, as well as the bearings, are manufactured with unavoidable tolerances, increasing the existing relatively large radial play of these component parts and contributing to the chatter of the window adjuster, particularly when the motor vehicle is subject to vibrations caused by uneven roads.
It is true that hinge mounts are known wherein attempts have been made to design a construction which is not susceptible to chatter or other noises. These known designs, however, even if not completely unsuccessful, have produced only partially satisfactory results. For example it is known to assign to the wobble gears a disk which is elastically supported on the eccentric. For this purpose, two bearing shells have been employed enclosing therebetween a ring-shaped body of an elastic material. By compressing such ring-shaped body, the existing tolerances were supposed to be eliminated and a play-free movement between the parts of the wobble gears was supposed to be achieved. Nevertheless, the rattling noises may still occur in this solution, inasmuch as the rattling can be avoided only when the radial load is lower than the restoring force resulting from the elasticity of the ring-shaped body.
In order to eliminate the radial play, another hinge mount of this kind has a section of its rotary shaft provided with a wedge-like surface surrounded by a sleeve-like portion of an eccentric member provided with an inclined surface cooperating with the wedge-like portion. The eccentric rotatably supports a spur gear assigned to one of the hinge mount levers of the adjuster. The rotary shaft is axially shiftable, and its wedge-like section is thrust by means of a spring assembly in the direction of increased eccentricity of the eccentric sleeve. By virtue of this spring-loaded eccentricity, it is possible to engage the teeth of the wobble gears without play, and consequently a chatter-free arresting of the adjusted position of the hinge mount levers is attained. Nevertheless, to enable the adjusting movement of the hinge mount lever connected to the backrest, a disengagement of the interlocked surfaces is necessary. This disengagement is carried out by axially displacing the rotary shaft until the wedge-like surface of its adjusting section is withdrawn from the sleeve-shaped eccentric member. The resulting advantage of an easy manipulation of the control handle during the adjusting or locking operation of the wobble gears, because of the cancellation of the play-free condition, necessitates however a large number of additional elements which must be arranged in a manner requiring relatively large installation space, thus increasing particularly the structural depth of the adjuster. In addition, the manufacture of these additional component parts and their installation are expensive and in many cases it appears that the expenditures for achieving the limited ease of control of the adjuster are unjustified.
In still another prior-art design of the adjuster for compensating the radial play of its hinge mounts, the rotary shaft is provided with a non-circular carrier section for transmitting the rotary movement to an eccentric member which is displaceable in radial direction towards its eccentric dimension. Between the eccentric member and the carrier section of the shaft there is provided an elastic buffer member, by means of which the part of the wobble gear mounted on the eccentric member is pressed into engagement with the teeth of the other wobble gear. Even in this solution, the compensation of the radial play is effective under the condition only that the radial load produced by the backrest is lower than the restoring force resulting from the elasticity of the buffer member. Moreover, this solution has the disadvantage that an amount of radial play desired for facilitating the adjusting movement is eliminated and consequently an increased resistance to the adjusting manipulation must be overcome.